Yes and it's a heavily experimental and not final spec called clientside quakec (csqc), the most hasslest thing to work on with quake ever.
Took a look at the specs. It's scope is wider than what I was planning.
CSQC is like quake3's cgame + ui qvms, where I'm only interested in the UI aspect (hud and menus).
My attitude to working on an engine is NOT to make the biggest greatest feature-packed shiniest bauble in the world, just something that works solidly on each platform and has some modest features. FWIW
P.S. seems one of the big differences in HL BSP is colored lightmaps.
That could be done in a SW renderer but I doubt it looks good.